SEER is a large population-based cancer registry database produced and maintained under NCI funding. SEER is a well known and valuable resource for epidemiological research on questions of cancer etiology, effectiveness of therapy, and related matters. CD-ROM is a revolutionary computer data storage medium that makes it possible for personal computers to inexpensively process large databases (650 megabytes per platter). This proposal is about making a CD-ROM product containing the seer database (and perhaps some related databases) for widespread distribution and processing on IBM compatible personal computers throughout the research community. This product (CD-SEER) will be prototyped in phase I and completed in the phase II SBIR grant period. The remarkable hardware and software developments of the past 5 years have made this task feasible, including: the development of CD technology and appropriate software to use it, including ISG's SearchLITE. Using SearchLITE, CD-SEER will enable a user to select a subset of records from SEER using familiar Boolean commands and then to view and process the selected data subset by using a spreadsheet or other appropriate analysis programs. These capabilities will make CD-SEER perform with the power of a mainframe epidemiological system, but at the cost and convenience of a personal computer.